Redundant If Statement and Regex

问题

The following code is clearly redundant, but in my experience I use this pattern fairly often. Is there some better way to do this in python?

if re.search("at (\d{1,2}):\d{2}", p):
    a=re.search("at (\d{1,2}):\d{2}",p).group(1)

回答1:

Yes, it is redundant; you should assign the result of search() to a variable instead of calling it twice:

m = re.search("at (\d{1,2}):\d{2}", p)

if m:
    a = m.group(1)

or maybe

a = m.group(1) if m else some_default_value

Also, if you're going to be using this pattern frequently, consider using re.compile() to pre-compile the regex.

回答2:

Save the first search and check its boolean meaning:

res = re.search (...)
if res:
   a = res.group (1)

来源：https://stackoverflow.com/questions/18625778/redundant-if-statement-and-regex